Automatic telephone system



Oct. 1, 1929. E. LOMAX AUTOMATIC TELEPHONE SYSTEM Original Filed July 13, 1925 Inusn U1" nus E. Lmnax Clare km. E

Patented Oct. 1, 1929 untrue STATES PATENT OFFICE CLARENCE E. LOMAX, OF CHICAGO, ILLINOIS, ASSIGN'OR, BY MESNE ASSIGNMENTS,

TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE Application filed July 13, 1925, Serial No. 43,089. Renewed December 17, 1928.

and the associated apparatus.

in telephone systems employing line finders, the total number of subscribers lines are divided into groups and each group of lines 'is served by a smaller group of finders. A distributor switch whlch is individual to the group of finders determines which one of the finders ot the group is to operate to find a certain calling line and connect it to an idle "trunk. One feature of this invention is concerned with that kind of finder system in which the finding operation consists of a primary and a secondary selecting operation to locate the calling line. A well known type of finder switch having a primary and a secondary selecting movement that may be employed, is the Strowger vertical and rotary switch. Finder switches of this general. type may be divided into two classes according to the manner in which the finder switch magnets are controlled, that is, receive impulses, assuming that Strowger vertical and rotary switches are used. One type, termed the fullselective type, is provided with an auxiliary vertical wiper and a row of contacts over which this vertical wiper passes during the vertical motion or" the switch. A certain potential placed on a certain one of these contacts, depending on the level of bank contacts in which the calling line terminates, determines the extent of the vertical motion of the switch wipers. After the vertical motion is completed the rotary motion takes place to select the terminals of a calling line, the extent of this rotary motion being likewise determined by a certain potential on one of the bank contacts of the calling line with which (a private wiper of the finder switch makes contact. The other type of finder switch, termed the full-directive type, has a sending mechanism associated with a group of finder switches which functions to send impulses to both finder switch magnets to operate a finder switch, first in its vertical motion, and then in its rotary motion. The number of impulses sent by the sending mechanism to the finder switch to operate the vertical and rotary magnets thereof, is determined by the number of the calling line with respect to its position in the line finder bank.

Both these types of finder switches have disadvantages; the full-selective type in that the auxiliary wiper arrangement contains certain mechanical difiiculties in regard to maintaining the proper adjustment thereof; the full-directive type in that the sending mechanism becomes complicated when means are provided to guarantee that the proper digits of the number of a certain calling line are sent, especially when two calls are initiated in the same group simultaneously.

In the present invention a new and improved finder switch system is produced which employs a finder switch of a type which may be termed the semi-directive type. In this finder switch system, impulses are sent to the vertical magnet of the finder switch by sending mechanism, which is common to the finders of one group. The number of im pulses sent is determined by the number of the level in which the calling line terminates in the line finder bank. The rotary motion, however, is not governed by impulses sent from a sender, but is controlled by a certain potential on the private bank contacts of noncalling lines over which a private wiper of the finder switch passes, and is stopped when the private wiper makes contact with the private bank contact of the calling line, a different potential existing on this bank contact at this time. By the employment oi this combination of methods for controlling the extent of the vertical and rotary motions of the finder switch, the disadvantages inherent to the fulldi ective and full-selective type described above have been eliminated. The provision of the auxiliary wiper and vertical bank for the finder switch have been obviated and the sending mechanism has been greatly sin plitied.

Another feature of the invention, relating to the sending mechanism, that the neces sity of restoring means for the sender wipers has been eliminated. A sender has been provided that sends out the proper number of digits regardless of the initial. position of the sender mechanism wipers on the sender mechanism bank contacts. This feature also prevents the proper operation of the sender being interfered with should an initiated call have been abandoned before the sender has had time to send its proper number of impulses. The sender, though then in a partially operated position,'will nevertheless send the proper number of impulses when another call is initiated.

Another feature of this invention relate to a revertively controlled arrangement whereby the length of the impulses transmitted to the vertical and rotary magnets of the finder switch is governed by that magnet to which the impulses are being sent. The magnets will automatically permit impulses to be transmitted at the maximum speed at which each can operate and thus the maximum speed of operation is attained without the possibility of the magnets losing an impulse.

These features and features relating to circuit details or other features not specifically mentioned. will be described more fully in the following specification, reference being had to the accompanying drawing.

Referring to the accompanying drawing, Fig. 1, there is shown, by means of the usual circuit diagram, a sufficient amount or the apparatus of a telephone system en'ibo-dying the principles of the invention to enable the invention to be understood and its utility appreciated.

The substation A is of the usual automatic type having two line conductors terminating at the automatic exchange. Individual to the line of substation A are the usual lino relay and cut-ofi relay, relay 5 and relay 4;. The total number of subscribers lines are divided into groups of approximately lines each which terminate in the banks of a group of connector switches whose banks are multiply connected together, and in the banks of a group of line finder switches whose banks are also multiplied together.

The line finder switch F is one of the group of finder switches in whose banks the line of substation A terminates. lilechanically the finder switch is similar to the well. known vertical and rotary step-by-stea switch having ten rows or levels of bank contacts with ten contacts in a level. The function of the finder switch is to find a calling line and connect it to the trunk leading to an idle succeeding switch.

Individual to this group of finder switches is the sender-distributor SD having sender switch which consists of the wipers 111 and 1l0 with their associated bank contacts and controlling circuits, and having a distributor switch which consists of the wipers 151156, inclusive, with their associated bank contacts and controlling circuits. hlechanically the sender switch is similar to the well known rotary line switch having twenty-five sets of contacts and having wi ers which have no normal position and move in a forward direction only, and which are moved on the backward stroke of a motor magnet. In the lower bank of the sender switch, the twelfth and twenty-fourth contacts (labeled 104 and 104; in the drawing) are connected to a battery supply. The level stop conductor, similar to conductor 102 of each of the ten lines terminating in the same level of the finder switch banks are multiplied together and connected to the contacts, whose number, counting in a counter clockwise direction from contacts 104 and 10%, corresponds to the number of that level. In the upper bank all the contacts except the twelfth (labeled 106 in the drawing) and thirteenth, and twentyfourth and twenty-fifth are connected to ground. The operation of the sender controls the extent of the vertical movement of the finder and is started when a subscriber initiates a e he start conductors, similar to conductor 101 of all the lines terminating in the be :m of the group of finder switches s 9 COlitllDll finder switch 5 are multiply con- L; nected to the common start conductor 101 of the sender distributor SD.

hlechauically, the distributor switch is also similar to the above typeof rotary switch= To each set of bank contacts except the last are connected the controlling conductors of one of the finders of a group. The function of the last set of contacts will be described later. After the finder has completed its hunting operation the distributor switch wipers are operated to connect the sending mechanism to the next idle finder switch of the group.

individual to each finder switch is a first selector permanently connected thereto. The first selector S, only the essential elements having to do with the operation of its associated finder switch being shown, is permanently connected to the finder switch F. The first selector S may have access to second selectors, which in turn may have access to other selectors depending on the size of the telephone system, the final selectors having access to connectors in the well known man ner, through which a call may be extended to .a subscribers substation.

Having described the system and the apparatus involved in general, a detailed description of its operation will now be given. F or this purpose it will be assumed that the subscriber at substation A, whose line it will be further assumed terminates in a set of contacts in the fourth level of the banks of the finder switches, wishes to establish a connection with some other subscriber in the exchange.

To establish a connection with a certain desired substation in the exchange, the subscriber at substation A removes his receiver and dials the directory number of that substation. VVhenthe receiver at substation A is removed, a direct current bridge is placed across the line conductors 2 and 3. A circuit is thereby closed for the line relay 5 which may be traced from ground by way of armature 9 and the resting contact, line conductor 2, the bridge at the substation A, line conductor 3, resting contact and armature 6, through the upper winding of line relay 5 to battery. Line relay 5 operates and places battery potential on the test contact 16 of the line tinder bank at armature 10 and the working contact, places ground on the level-stop conductor 102 at armature 11 and the working contact, and places ground on the start conductor 101 at armature 12 and the working contact. The levelstop conductor 102 is connected to conduct-or 102 which is common to the ten substations whose lines terminate in the fourth level of line finder bank contacts of the particular group shown. Gonductor 102 is connected to the fourth bank contacts of the sender mechanism counting in a counter-clockwise direction from contacts 10% and 104, respectively, and governs the number of impulses to be sent to the finder switches, as will be fully understood from the following description.

A circuit may now be traced from ground by way of the resting contact and armature 8, armature 12 and a working contact, start conductor 101, start conductor 101, resting contact and armature 1 18, interrupter springs 130, through the winding of the stepping relay 120 to battery. Stepping relay 120 operates and closes a. circuit for the motor magnet 127 at armature 132, which may be traced from ground by way of a rmature 36 and the resting contact, conductor 150, resting contact and armature 141, armature 132 and the working contact, through the winding of motor magnet 127 to battery. The operation of the other armatures of relay 120 has no utility at this time. Motor magnet 127 operates and opens the circuit of stepping relay 120 at its interrupter springs 130. This causes the deenergization of the stepping relay 120, which in turn opens the circuit of the motor magnet 127 at armature 132. In releasing its armature, the motor magnet 127 moves the sender switch wipers 110 and 111 to the next set of bank contacts. The deenergization of the motor magnet 127 again closes the circuit of stepping relay 120 at the interrupter contacts 130. tepping relay 120 energizes a second time and again closes the circuit for the motor magnet 127 at the armature 132. Motor magnet- 127 operates a second time.

This alternate operation-of the stepping relay 120 and the motor magnet 127 continues and each time the motor magnet 127 releases, the wipers 110 and 111 are advanced one step. Conductor 150 is common to all the finder s itches of one group. Therefore ground is supplied to this conductor by the resting contact of the armatures corresponding to armature 36 of all the finder switches or the asso ciated group, which are idle. Consequently if finder switches of the group are busy there will be no ground on conductor 150. The operation of the motor magnet 127 is thus prevented it no finder of the group is idle.

W hen the wiper 111 reaches bank contact 103 to which ground is now supplied by way of the resting contact and. armature 7, armature 11 and the working contact, level-stop conductor 102, level-stop conductor 102, a circuit is closed for the pick-up relay 121 which may be traced from ground on the bank contact 103, wiper 111, through the winding of the pick-up relay 121, through the resistance 150 to battery. Pick-up relay 121 energizes and prepares the impuising circuit for the vertical magnet of the finder switch at armature 13 1 and the working contact, prepares the revertively controlled locking circuit for stepping relay 120, to be described later, at armature 135 and the wor'. ing contact, closes a locking circuit tor itself to the grounded conductor 101 at armature 136 and the working contact, and closes a circuit for the slow acting relay 122 at armature 137 and the working contact. The next time the stepping relay 120 operates, the impulsing circuit is closed at armature 131 and the working contact. A circuit for the vertical magnet 28 of the finder switch F may now be traced from ground on the contact 105 of upper bank of the sender switch, wiper 110, working contact and armature 131, armature 13 1 and the working contact, wiper 155, bank contact 165 of the distributor switch. it being assumed that the wipers 151456, inclusive, are now resting on bank contacts 161-166, inclusive, conductor 17 to the Ycrtical magnet 23 of tinder switch F to battery. In operating, stepping relay 120 also closes the revertively controlied locking circuit for itself at armature 133, which may be traced from ground by way of the resting contact and armat re 1410, armature 1 16 and the resting contact, wiper 151, bank con act 161, interrupter sprii gs 11, interriugser springs 12, conductor 17 3, bank con 163, wiper 153, armature 1 2 and the re tact, the working contact and arnia'ti e 13 armature 133 and the work v; co through the winding of the .rt L 120 to battery. This locking circuit is 1? id closed until the vertical ma t has practically completed its strol-te which thus the locking circuit is opened at the intcrriuiter springs 42. Tnthis manner the circuit of the vertical magnet is maintained closed as long as it is necessary for the complete operation of the vertical magnet.

During this time the motor magnet 127 is in an operated position and maintains the initial energizing circuit of stepping relay 120 open at the interrupter springs 130. As soon as the locking circuit of stepping relay 120 is opened at the interrupter spring 42 by the action of the vertical magnet 28, the stepping relay 1.20 is allowed to deenergize thereby opening the circuit of the motor magnet 127 which in turn deenergizes to advance the switch wiper another step. In deenergizing, the motor magnet 127 again closes the initial circuit for the stepping relay 120 at the interrupter springs 130, and the above operation again. repeats itselt'. Thus it will be seen that the speed or operation of the stepping relay 120 and the motor i'nagnet 127 is gov erncd by the natural speed of operation of the vertical magnet 28, which. is the maximum speed at which. the vcrti "a1 magnet can be made to operate. Since the pick-up relay 121 is locked in an operated. position, the circuit for the vertical magnet is maintained closed at armature 134 and the working contact previously described. Each time the stepping relay 120 operates and closes its armature 131, an impulse of ground is sent to the vertical magnet 28 until the switch wiper 110 is moved to the ungrounded bank contact 106, at which time no more impulses will be sent to the vertical magnet 28. The wiper 111 Will also be resting on bank contact 104 and thereby short circuit the winding of the pickup relay 121 over an obvious path including the impulse stop conduct-or 100. Short circuiting the pick-up relay 121 causes it to deenergize and release its armatures.

W hen the pick-up relay 121 first operated it closed a circuit for the slow-acting relay 122, which operated to prepare a circuit for the stepping relay 124 at the armature 138 and the working contact, and to prepare a circuit for the upper winding of the cut-over relay 123 at armature 139 and the working contact. Relay 122 is slow acting and will maintain its armatures in an operative position for an interval after the circuit is opened at armature 137 and the working contact by the release of the pick-up relay 121. Therefore, when the pick-up relay 12'1 deenergizes, an initial circuitis completed for the stepping relay 124 from ground by way of armature 137 and the resting contact, armature 138 and the working contact, through the winding of the stepping relay 124 to battery, and an initial energizing circuit is completed for outover relay 123 from ground by way of armature 137 and the resting contact, armature 139 and the working contact, through the upper winding of? the cut-over relay 123 to battery. Cut-over relay 123 energizes and by the operation of armatures 140 and 142 trans nvzavas fers the revertively-controlled locking circuit from the stepping relay 120 to the stepping relay 124, the utility of which will again be described shortly. The operation of armature 141 opens the energizing circuit of the motor magnet 127 thereby preventing any further operation of the magnet. At armature 143, cut-over relay 123 closes a locking circuit for itself from ground on the conductor 101, resting contact and armature 148, armature 147 and the resting contact, armature 143 and the working contact, through the lower winding ot'cut-over relay 123 to battery. Stepping relay 124 operates and closes, at its armature 144 and the working contact, the revertively-controlled locking circuit which may now be traced from ground by way of armature 144 and the working contact, armature 146 and the resting contact, wiper 151, bank contact 161, conductor 171, interrupter contacts 41, interrupter contact 42, conductor 173, bank contact 163, wiper 153, armature 142 and the working contact, through the winding of the stepping relay 124 to battery. Upon energizing, stepping relay 124 also closes a circuit for the rotary magnet 27 which may be traced from ground by way of the working contact and armature 145, wiper 154, bank contact 164, conductor 174, through winding of rotary magnet 27 to battery. This circuit is maintained closed as long as the stepping relay 124 remains in an operated position. Stepping relay 124 in turn is locked in an operated position over the revertivelycontrolled circuit which remains closed until the rotary magnet 27 has practically completed its stroke. Near the end of the stroke, the rotary magnet 27 opens a point in the revertively-controlled locking circuit at interrupter springs 41. Stepping relay 124 then deenergizes and opens the circuit of rotary magnet 27 at armature 145.

The finder switch wipers 21, 22, and 23, have now been rotated into engagement with the first set of bank contacts in the fourth level. It is assumed that the bank contacts 15, 16, and 17 which terminate the line to the substation A, do not appear as the first set of bank contacts-in-the fourth level, and itis turther assumed that the substation whose line terminates in the first set of ban 1 contacts is not attempting to make a call at this very same instant. Under these conditions ground potential will be present on the private test contact of this first set 01'' contacts similar to test contact 16, either by way of the resting contact and an armature similar to armature 10 (it the corresponding substation is idle), or by way 01 a private normal conductor from a connector bank similar to conductor 200 at armature 10 in an operated position (if the corresponding substation has had a call extended to it) as is well known in the art, or by another test contact similar to contact 16, of another finder switch bank being used in an established connection, and multipled to test contact 16 (if the corresponding substation has established a connection with another substation). When the private wiper 22 comes in contact with this bank contact upon which there is ground potential, a circuit is closed for the stepping relay 12-1 which may be traced from ground on the said test con tact, test wiper 22, armature and the resting contact, interrupter springs l1, interrupter springs 1-2 conductor 1721, contact 163, wiper 153, armature l i-2 and the working contact, through the winding of the stepping relay 12% to battery. liltepping relay 12-l energizes and again closes the revertivelycontrolled locking circuit for itself at armature 1 14, and closes the circuit for the rotary magnet 27 at armature 14-5 and the working contact. Rotary magnet 27 operates and near the end of its stroke opens the locking circuit of stepping relay 12% at the interrupter contacts 11. Stepping relay 124 deenergizes and 36115 the circuit for the rotary magnet 27. Upon deenergizing, rotary magnet moves the finder switch wipers 21, 22, and 23 to the next set of bank contacts. if this second set of bank contacts terminates the line of another idle substation or a substation which is busy by reason of an established connection, ground will again be present on the private bank contacts as previously described. BO tary magnet 27 will again be operated to rotate the switch wipers 21, 22 and 23 to the third set of bank contacts in the fourth level.

The above described action will be repeated and the wipers 21, 22 and 23 will be moved from one set of bank contacts to the next until they come in contact with the set of bank contacts which terminate the line of a calling substation. If this happens to be some other line which appears before the line of substation A in the bank of the finder, the finder switch F will find this other calling line and proceed to extend its connection. The line of the calling substation A will then be found by the next idle finder switch under the control of the selector distributor SD as will be understood from subsequent descrip tions.

It will be assumed however that the line of substation A terminating in the bank contacts 15, 16 and 17 is the first line terminating in the fourth level which is initiating a call at this time. When the finder switch wiper 22 comes in contact with bank contact 16, no circuit will be closed for the stepping relay 12 1. Consequently no circuit wi l be closed for the rotary magnet 27 which therefore will not operate and the wipers 21, 22 ant 23 will come to rest on bank contacts 15, 16 and 17 respectively.

Bearing in mind that line relay 5 and the slow-acting relay 26 are now in an operated position, a circuit may be traced for the switching relay 25 of the finder switch F from ground by way of armature 38 and the working contact, through the winding of switching relay 25, interrupter springs ll, interrupter springs 42, conductor 173, con tacts 163, wiper 153, armature 14:2 and the working contact, through the winding of the stepping relay 12 1 to battery. Stepping relay 12% will not operate in series with the switching relay 25. Switching relay 25, how ever, operates in series with the stepping relay 124 and closes a locking circuit for itself at armature 33 and the working contact to battery through the resistance 180, opens a point in the circuit of the release magnet 29 at armature 32, places ground on conductor 172 at armature 36 and the working contact, and closes a circuit for the switching relay 1 and the line 5 in series at armature 34: which may be traced from ground at armature 3S and the working contact, working contact and armature 34:, wiper 22, test contact 16, armature 10 and the working contact, through the lower winding of the switching relay 4: and through the lower winding of the line relay 5 to battery. Switching relay 1 operates and disconnects ground from the start conductor 101 and the level-stop conductor 102 at armatures 8 and 7, respectively, and dis connects ground and battery from the line conductors 2 and 3 at armatures 9 and 6, respectively. Line relay 5 is held operated over its lower winding.

As result of the placing of ground on conductor 172, a circuit is closed for the guard relay 125, which may be traced from grounded conductor 172, bank contact 162, wiper 152, through the winding of guard relay 125 to battery. A circuit is also closed for the stepping magnet 126 in parallel with the guard relay 125 by way of interrupter springs 149, through the winding of the stepping magnet 126 to battery. The stepping magnet 126 operates, opens its circuit at the interrupter springs 149, and then releases, stepping the wipers 151 to 156, inclusive, to the next set of bank contacts. If the finder switch whose controlling conductors similar to conductors 172176, inclusive, terminate in the next set of bank contacts is busy, ground will also be present on the test conductor similar to conductor 172 and a circuit will again be closed for the stepping magnet 126. Consequently the stepping magnet 126 will operate to step the switch wipers 151-156 inclusive, over the bank contacts until an idle finder switch is reached. Guard relay 125 is maintained energized during this hunting operation from ground on the busy contacts representing busy finder switches encountered by the wiper 152, wiper 152 being wide enough to touch the next contact before it entirely leaves the preceding contact. Relay 125 operates and removes ground from the wiper 151 at armature 146, unlocks the cut-over relay 123 by opening the circuit of tween him and the calling subscriber at substation A may take place. Atthe termination of the conversation, both subscribers will replace their receivers on their respective switchhooks. This causes the release of certain relays in the connector associated with the connection, which removes ground from the holding conductors of the preceding switches including conductor 60. The release of the switching relays of the selectors associated with the connection including switching relay 53, the switching relay 25 of the finder switch F and also the release of the switching relay 4 and the line relay 5 is thereby eii'ected. The release of the switching relay 53 and of the switching relays of the other selectors associated with the connection closes circuits for release magnets (not shown) which restore the respective selectors to normal. On releasing, switching relay 25 restores its armatures and closes a circuit for the release magnet 29 at armature 32, which may be traced from ground by way of armature 38 and the resting contact, armature 32 and the resting contact, off-normal springs 43 which were closed upon the first vertical step of the shaft of the finder switch F, through the winding of the release magnet 29 to battery. Release magnet 29 operates to displace the dog which holds the switch wipers in position and thereby allows the switch wipers of the finder switch F to restore to normal.

In order to explain the operation of the switching relay and line relay which are individual to asubstation when a substation is being called, it will be assumed that a certain calling subscriber is attempting to obtain connection with the subscriber at substation A. When the calling subscriber has completed dialling, his connection having been extended through a find-er switch and one or more selectors to a connector of the group of connectors in whose banks the line of substation A terminates, ground will be supplied to the private conductor 200. A circuit will be closed for the switching relay 4 and the line relay 5 in series, through the winding of relay 4 and through the lower winding of relay 5 to battery. Switching relay 4 energizes and disconnects the line conductors 2 and 3 from their normal ground and battery connections at armatures 9 and 6, respectively, and disconnects ground from armatures 7 and 8 by separating them from their respective resting contacts. Line relay 5 energizes and supplies ground to test contact 10 (and all other test contacts multipled to contact 16 in the banks of the other finder switches of the group) at armature 10 and the working contact, from the grounded private conductor 200. The operation of armatures 11 and 12 is of .no avail at this time since armatures 7 and 8 are in an operated position.

When the subscriber at substation A removes his receiver to answer the call, no further operation, other than the operation of a relay in the associated connector, takes place, and the two subscribers may immediately being conversation. lVhen the conversation is ended, both subscribers re-' place their receivers on their respective switchhooks and the switches associated with the connection are released. Ground is removed trem the private conductor 200, and relays 4 and 5 are decnergized, restoring their arina-tures back to normal. The apparatus is new in condition to receive or extend another call.

In a previous paragraph in this specification it was stated that no restoring means for the sender mechanism wiper is necessary because the sender switch employed always sends out the proper number of digits regardless of the starting position of the sender switch wipers. A short explanation of this feature will now be given. As previously described, the wipers 110 and 111 are rotated over the respective bank contacts when ground placed on the start conductor 101. No impulses are sent to the vertical magnet, however, until the pick-up relay 121 is operated. This relay will not operate until the wiper 111 reaches the contact 103 again assuming that the particular calling station line terminates in the fourth level of the finder switch banks. Therefore it is evident that the switch wipers 110 and 111 may be resting on any contact between the one upon which wiper 111 is resting as shown in the drawing and contact number 103, without effecting the sending of impulses to the vertical magnet. Should the wiper 111 be resting on the contact 103 when the call is first initiated, the pickup relay 121 will of course operate immediately and impulses will be sent to the vertical magnet immediately. Should, however, some subscriber previously have initiated a call but for some reason abandoned the attempt before the switch wiper 111 reached the contact 104, switch wiper 111 would be stopped on one of the contacts between contact 103 and contact 104-, by the removal of ground from the start conductor 101 which occurs when a calling subscriber replaces his receiver and deenergizes the line relay 5. It a call be initiated with the wiper in this position, the wipers must be rotated to contact 103' before the pickup relay can be operated, after which impulses will be sent to the vertical magn ct as before. Thus it will be seen that no restoring means are necessary for the sender mecha nism wipers. The proper number of digits will be sent regardless of the initial position of the sender switch wipers.

In the foregoing paragraphs, a finder switch having bank contacts placed in hori- Zontal rows or levels and having ten such levels and ten contacts in. a level has been de scribed. I is to be understood of course that since the rotary motion of the switch wipers is a self-actuating operation, similar to the rotary motion of any standard vertical and rotary step by step switch, the number of contacts existing in a level or the number of levels are not limited to any specific number. Neither is the finder switch limited to the requirements of having only one set of wipers. A double set of banks and a double set of wipers, one set for each set of banks may be provided thereby doubling the capacity of the finder switch. In this case, not only the extent of the rotary motion but also the election of the set of switch wipers to be employed would be governed by a particular potential existing on the private bank cont-acts. An arrangement similar to this as cescribed above and easily appliable to the present finder switch, is disclosed in the copendinp' application oi T. G. ll lartin, filed May 10, 1923, Serial No. 63?,931, patent No. 1,564,487, Dec. 8, 1925.

What is claimed is:

1. In a telephone system, a finder switch having primary and secondary movement, an individual test wiper for said finder, a sender switch common to said finder and other similar finders, a test wiper for said sender switch, and circuit arrangements whereby the primary movement of said finder is controlled by the sender test wiper, while the secondary movement is controlled by the indi vidual test wiper.

2. In a telephone system, a group of finders each having a primary and a secondary movement, testing means common to said finders for controlling the primary movement of any finder, and individual testing means in each finder including only a single wiper thereof for controlling its secondary movement.

3. In a telephone system, a group of two motion finders, a control switch common to said finders, means for determining the primary movement of any finder in accordance with a designated contact in the bank of said control switch, and means for determining the secondary movement of any finder in accordance w th a designated contact in the bank of the finder concerned l. In a telephone system, a two-motion finder switch, a calling line terminating in the bank thereof, a primary and a secondary magnet for propelling said finder switch in its respective movements to find said calling line, a sending mechanism common to said finder switch and to other similar finder switches for sending a predetermined number of impulses to operate said primary magnet depending on the level of the bank in which the calling line terminates and a stepping relay for sending impulses to operate said secondary magnet to find the calling line.

5. In a telephone system, a two-motion finder switch having a wiper, a plurality of contacts consecutively engaged by said wiper, a sender switch associated with said finder switch having a second wiper, a plurality of contacts engaged by said second viper, a steppin relay in the sender switch for transmitting impulses to operate said finder switch in its primary movement, means for determining the extent of said primary movement depending on which of said second plurality of contacts a characteristic potential exists, a second stepping relay for transmitting impulses for operating said finder switch in its secondary movement, and means for de termining the extent of said secondary movement depending on which of said first plurality of contacts a characteristic potential exists.

6. In a telephone system, a two-motion finder switch having a wiper, a plurality of contacts consecutively engaged by said wiper, a sender switch associated with said finder switch having a second wiper which remains in the position last used, a plurality of contacts consecutively engaged by said second wiper, means for placing a characteristic potential on one of said first plurality of contacts, means for placing a characteristic potential on one of said second plurality of contacts, means for causing the sender switch to operate said finder switch in its primary motion, means for determining the extent of said primary motion independent of the number of consecutive contacts engaged by the second wiper but depending on which of said second plurality of contacts said characteristic potential exists, means for operating said finder switch in its secondary motion, and means for determining the extent of said secondary motion depending on which of said first plurality of contacts said characteristic potential exists.

7. In a telephone system, a two-motion finder switch, a magnet for operating said finder switch in its primary movement, means for operating said finder switch in its secondary movement, a sending mechanism including a counting switch and two wipers, means including one of said wipers of said sending mechanism for sending impulses to said magnet and including the other of sait wipers for determining the number of impulses to be sent to determine extent ot said primary movement, and means including a wiper of said finder switch for determining the extent of the secondary movement.

8. In a finder switch system for use in telephone systems, a finder switch, a sending mechanism associated with said finder switch, a magnet for operating said sending mecha nism, a relay'tor controlling the operation of said magnet, a circuit for said relay in eluding contacts on said magnet, an operating magnet for said finder switch, and an auxiliary circuit for said relay including contacts on said finder switch magnet.

9. In a telephone system, a two motion finder switch, a magnet for operating said finder switch in its primary motion, a second magnet for operating said finder switch in its secondary motion, a sending mechanism as sociated with said finder switch, a third magnet for operating said sending mechanism to send impulses to said first magnet, a relay for controllin the operation of said third magnet, a circuit for said relay including contacts on said third magnet, an auxiliary circuit normally includino' said relay and including contacts on said first and said second magnet, a stepping; relay for controlling the operation of said second magnet, and means for transferring said auxiliary circuit from aid first relay to said stepping relay.

10. in a finder switch system for use in telephone systems, a group of finder switches, a magnet for each finder switch, a sender switch, means for associating" said sender switch with an idle one of said finder switches, a magnet for operating said sender switch, a relay for controlling the operation of said magnet, a circuit for saic relay including contacts on said magnet, and an auxiliary circuit for said relay including contacts on the magnet 01 the associated finder switch.

11. In telephone system, calling lines di vided into groups, a line finder switch in the hanl-r of which said lines terminate, a finder ailctter i r preselecting said finder switch, a sender switch individual to and opcratively connected with said finder allotter, said sendcr switch set motion by the initiation of a call from any line and effective over the said preselected connection to directively operate the said finder into selective relation with the line group in which the calling; line is located and testing means in the finder for causing the same to select the terminals of the line calling.

123. in a telephone system, a finder allotter having wipers, a finder switch preselected by said allotter, groups of lines terminating in bank contacts of said switch, a control switch temporarily associated with said finder switch through the wipers of said allotter, means in said control switch responsive to the initiation of a call on any line and etiective to directively control the finder to cause the same to be positioned into selective relation with the group of lines in which the calling line is located and neans in the finder switch for causing the same to hunt for and seize the terminals ol the calling line.

13. in a telephone system, a group of finders each having a primary and a secondary movement, a finder allotter having wipers, means for operating said allotter to preselect an idle one or" said finders, a switch common to said finders effective while operating to control the primary movement of any finder over the wipers of said allotter, and individual testing means in each finder for controlling its secondary movement.

let. In a telephone system, two motion finder switches, coups of calling lines terminating in be; oi? said finder i contacts switches, a controlling switch common to said finder switches, a finder allotter having wip ers for associating a control switch with a finder switch, means responsive to the initiation of a call over any line to cause the con trolling switch to dircctively operate the associated finder switch over said wipers into selective relation to the group in which the calling line is located, and means for thereafter causing the finder switch to hunt for and connect with the calling line.

15. In a telephone system, a finder switch having a primary motion and a secondary motion, a sender switch associated with said finder switch, means includ'ngr a wiper oi? said sen-.iier switch for a plet-inn; a circuit over which impulse are transmitted to the finder to operate the finder its rimary motion, iii-cans within said sender f .tch for controlling the extent of said primary vement, and means within said finder switch for controlling the extent of said secondary move ment.

16. In a telephone system. a finder switch having primary and secondary movements, a sender switch, two impulsingrelays in said sender switch for transmitting impulses tor operating said finder switch in both movements, one impulsing relay for each move ment, means within said sender switch for controlling the extent of said primary movement, and means within said finder switch for controlling the extent of said secondary movement.

17. In a. telephone system, a finder switch having a primary and a secondary movement, impulsinp; relays vithout said switch transmitting impulses tor operating sa d switch in both movements, one iinpulsinp; relay tor each movement, means without said switch for controlling the extent of mary movement, and means within said switch tor controlling; the extent of said secondary movement.

18. in a telephone system, a two-motion finder switch, an auxiliary switch, two impulsingz' relays in said arxi iary switch for transmittin impulses to said finder switch to operate it in ho -h its motions. one impulsrelay for each motion, and within said two-motion switch for controlling the speed at which said relays transmit impulses.

19. In a telephone system, a two-motion finder switch, an auxiliary switch, means in cluding a wiper of said auxiliary switch and imp ulsing relays within said auxiliary switch for transmitting a series of impulses to said two-motion switch for each motion, one impulsing relay for each series of impulses, means including a second wiper of said auxiliary switch for determining the number of impulses to comprise the series. transmitted for the first motion, and means within said two-motion switch for determining the number of impulses to comprise the series transmitted for the second motion.

20. In a telephone system, a two-motion finder switch, an auxiliary switch, means within said auxiliary switch for transmitting a series of impulses to said two-motion switch for each motion, means within said auxiliary switch for determining the number of impulses to comprise the series transmitted for the first motion, means within said two-motion switch for determining the number of impulses to comprise the series transmitted for the second motion, and separate means within said two-motion switch for controlling the rate of speed at which each series of impulses is transmitted.

21. In a telephone system, a two-motion finder switch, means including two impulsing relays for transmitting series of impulses to said switch, one relay and one series for each motion, means without said switch for determining the number of impulses to comprise the series for the first motion, and means within said switch for determining the number of impulses to comprise the series for the second motion.

22. In a telephone system, a finder switch, means for transmitting two series of impulses to said switch, means without said switch for determining the number of impulses to comprise the first series, means within said switch for determining the number of impulses to comprise the second series and separate means within said switch for controlling the rate of speed atwhich each series of impulses is transmitted.

23. In a telephone system, a two-motion finder switch, a magnet for operating said finder switch in its primary movement, a sending mechanism having a counting wiper and contacts engaged thereby, and means for sending a predetermined number of impulses to said magnet regardless of the starting position of said wiper with respect to said contacts.

24. In a telephone system, a two-motion finder switch, a magnet for operating said finder switch in its primary movement, a sending mechanism having two wipers and two rows of contacts, means for operating said wipers to pass over said rows of contacts respectively, an impulsing circuit for said magnet including one of said wipers, and means including the other of said wipers and a predetermined contact of the row associated with said other wiper for closing said impulsing circuit.

25. In combination, a two-motion finder switch having a stepping magnet, a counting device having a stepping magnet, a relay for transmitting impulses to said magnets simultaneously, and a circuit for said relay having two branches controlled by said two magnets, respectively.

26. In combination, a two-motion finder switch having a stepping magnet, a counting device having a stepping magnet, a relay ior transmitting impulses to said magnets simultaneously, an energizing circuit for said relay controlled by one of said magnets, and a locking circuit for said relay controlled by the other of said magnets. 7

27. In combination, a two-motion finder switch having a stepping magnet, a counting device having a stepping magnet and a relay, a circuit over which said relay transmits impulses to said second magnet to operate said counting device, a circuit for said relay controlled by said second magnet, a normally open circuit for enabling said relay to send impulses to said first magnet, a normally open circuit for said relay controlled by said first magnet, and means responsive to a pre determined extent of operation of said counting device for closing said last two circuits.

28. A driving arrangement for a two-motion finder switch comprising two magnets, two stepping relays associated with. said magnets, respectively, a circuit including serially related contacts on said magnets and normally including a first one of said relays, and means for substituting the second relay for the first in said circuit.

In witness whereof, I hereunto subscribe my name this 10th day of July, A. D. 1925.

CLARENCE E. LOMAX. 

